HEDSTRAND , U., S. JAKOBSON, U. NYLUND, and H. STERNER. “The Concordance of Respiratory Fluctuations in Oesophageal and Central Venous Pressures”. Upsala Journal of Medical Sciences, vol. 81, no. 1, June 1976, pp. 49-53, doi:10.3109/03009737609179021.